Monday, October 13, 2014

LRO: widespread evidence of young lunar volcanism

The feature called Maskelyne is one of many newly discovered young volcanic deposits on the Moon. Called irregular mare patches, these areas are thought to be remnants of small basaltic eruptions that occurred much later than the commonly accepted end of lunar volcanism, 1 to 1.5 billion years ago [NASA/GSFC/Arizona State University].
Dwayne Brown
NASA HQ

NASA’s Lunar Reconnaissance Orbiter (LRO) has provided researchers strong evidence the moon’s volcanic activity slowed gradually instead of stopping abruptly a billion years ago.

Scores of distinctive rock deposits observed by LRO are estimated to be less than 100 million years old. This time period corresponds to Earth’s Cretaceous period, the heyday of dinosaurs. Some areas may be less than 50 million years old. Details of the study are published online in Sunday’s edition of Nature Geoscience.

“This finding is the kind of science that is literally going to make geologists rewrite the textbooks about the moon,” said John Keller, LRO project scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland.

The deposits are scattered across the moon’s dark volcanic plains and are characterized by a mixture of smooth, rounded, shallow mounds next to patches of rough, blocky terrain. Because of this combination of textures, the researchers refer to these unusual areas as irregular mare patches.

The features are too small to be seen from Earth, averaging less than a third of a mile (500 meters) across in their largest dimension. One of the largest, a well-studied area called Ina, was imaged from lunar orbit by Apollo 15 astronauts.

Ina appeared to be a one-of-a-kind feature until researchers from Arizona State University in Tempe and Westfälische Wilhelms-Universität Münster in Germany spotted many similar regions in high-resolution images taken by the two Narrow Angle Cameras that are part of the Lunar Reconnaissance Orbiter Camera, or LROC. The team identified a total of 70 irregular mare patches on the near side of the moon.

The large number of these features and their wide distribution strongly suggest that late-stage volcanic activity was not an anomaly but an important part of the moon's geologic history.

The numbers and sizes of the craters within these areas indicate the deposits are relatively recent. Based on a technique that links such crater measurements to the ages of Apollo and Luna samples, three of the irregular mare patches are thought to be less than 100 million years old, and perhaps less than 50 million years old in the case of Ina. The steep slopes leading down from the smooth rock layers to the rough terrain are consistent with the young age estimates.

In contrast, the volcanic plains surrounding these distinctive regions are attributed to volcanic activity that started about 3 1/2 billion years ago and ended roughly 1 billion years ago. At that point, all volcanic activity on the moon was thought to cease.

Several earlier studies suggested that Ina was quite young and might have formed due to localized volcanic activity. However, in the absence of other similar features, Ina was not considered an indication of widespread volcanism.

The findings have major implications for how warm the moon’s interior is thought to be.

An oblique, novel view of the Ina formation (3 km across, 18.65°N, 5.3°E) from the LROC narrow angle camera (resolution 2.5 meters per pixel [NASA/GSFC/Arizona State University].
“The existence and age of the irregular mare patches tell us that the lunar mantle had to remain hot enough to provide magma for the small-volume eruptions that created these unusual young features,” said Sarah Braden, a recent Arizona State University graduate and the lead author of the study.

The new information is hard to reconcile with what currently is thought about the temperature of the interior of the moon.

“These young volcanic features are prime targets for future exploration, both robotic and human,” said Mark Robinson, LROC principal investigator at Arizona State University.

LRO is managed by Goddard for NASA’s Science Mission Directorate at NASA Headquarters in Washington. LROC, a system of three cameras, was designed and built by Malin Space Science Systems and is operated by Arizona State University.

To access the complete collection of LROC images, visit http://lroc.sese.asu.edu/

For more information about LRO, visit http://www.nasa.gov/lro

Some Related Posts:
Hansteen α -   January 15, 2014
Small-scale volcanism on the lunar mare, July 13, 2013
New views of the hollows of Rimae Sosigenes, March 28, 2013
Inside Rima Hyginus, June 12, 2012

Thursday, September 25, 2014

Below is a posting for post-doc position at LLNL

The Chemical Sciences Division (CSD) in the Physical and Life Sciences (PLS) Directorate is seeking a planetary sciences postdoctoral researcher. This position requires US citizenship.  

The successful candidate will contribute to several research projects funded by NASA, as well to projects funded by the Department of Energy.  NASA related projects will address the origin and evolution of primordial Solar System condensates, primitive meteorites, lunar samples, and martian meteorites. 

The candidate is expected to have experience with  chemical separation by ion chromatography in a class 100 clean room environment, as with as with isotopic analyses by either multi-collector inductively coupled or thermal ionization mass spectrometry.  This individual will report to the Group Leader for Chemical and Isotopic Signatures.  

Send CV to Lars Borg (borg5@llnl.gov) or Ian Hutcheon (hutcheon1@llnl.gov).

Tuesday, March 11, 2014

Modified Craters of Moscoviense

Morning light beams over the walls and peaks of an irregularly shaped crater in Mare Moscoviense. This unnamed crater is approximately 17 km in diameter; portion of controlled NAC Mosaic MOSCOVNSLOA, downsampled for web browsing [NASA/GSFC/Arizona State University].
J. Stopar
LROC News System

This crater is one of several similarly shaped craters in Mare Moscoviense. These craters are pockmarked by craggy peaks and fractured floors. The dramatic illumination in the opening image, with the sun low on the horizon, exaggerates the crater's lumpy topography.

This crater, and others like it, represent one type of volcanically modified impact crater. The floor of the crater, shown in detail below, is not much below the surface of the surrounding volcanic plains, and looks nothing like a typical fresh impact crater, such as Giordano Bruno or simple bowl-shaped crater like this one on the farside. Sharp boundaries with flat-lying mare basalts around the crater rim (arrows) indicate where the crater was once surrounded (embayed) and nearly covered by large outpourings of lava. Only the upper part of the crater rim remains.

Unnamed 17km diameter crater in Mare Moscoviense, located at 146.391°E, 26.805°N. Arrows indicate extent of mare embayment. Click on the image for a higher resolution view of the crater floor [NASA/GSFC/Arizona State University].
How did this crater get so lumpy inside? Did volcanic materials push up from beneath the crater floor? Did molten lava intrude through fractures or low points in the crater rim and walls? Did the heat of nearby lava and magma deform the crater like hot plastic? The answer may be a combination of these processes, though most scientists think that the changes in crater shape occur mainly as a result of magma intruding from below.

HDTV still from Japan's lunar orbiter SELENE-1 (Kaguya) show the horizon to horizon extent of Mare Moscoviense, now known to be an unusually thin part of the Moon's crust in the farside lunar highlands. The view is from the north, from an altitude of about 100 km. The wallpaper-sized original can be viewed HERE [JAXA/NHK/SELENE].
Explore this crater and two more like it in entire NAC mosaic, HERE.

Re-visit these other volcanically modified impact craters:

Thursday, March 6, 2014

Squarish Levoisier A of Oceanus Procellarum

Squarish Lavoisier A
The square corner along the north-most rim of Lavoisier A (28.5 km, 36.972°N, 286.74°E), evidence of pre-impact fracturing. LROC NAC observation M112759713L, spacecraft orbit 18324, July 4, 2014; field of view approximately 7 km, resolution 1.41 meters per pixel. LROC Featured Image, released March 6, 2014 [NASA/GSFC/Arizona State University].
Raquel Nuno
LROC News System

Why are most craters circular (even craters found on Earth)? By hurtling objects together at many miles per second in large laboratories, scientists have shown that only the most oblique impacts (less than 10° from the horizon) produce elliptical craters.

The kinetic energy of an impactor behaves much like the energy from a nuclear bomb. The energy is transferred to the target material by a shock wave, and shock waves produced by an impact, whether oblique or head-on, propagate hemispherically. This shape means that energy is being delivered equally in all directions; resulting in a hemispherical void and thus circular craters. However, conditions in nature do not always mirror the laboratory. In fact some craters are nearly square! A portion of the rim of Lavoisier A crater tells a story of the geology before impact. Lavoisier A is a squareish crater with a diameter of 28.5 km in the northwestern portion of Oceanus Procellarum.

Levoisier A from Chang'e-2
High-reflectance, low-angle illumination incidence view of 28.5 km-wide Levoisier A from the Chang'e-2 global mosaic, with real color added from the Clementine survey (1994) [Virtual Moon Atlas 5].
Much of Lavoisier A's shape is thought to be due to preexisting joints or faults in the target rock. These discontinuities create zones of weakness, affecting how the shock wave travels through the material. We find square craters on other planetary bodies such as on the asteroid Eros and here on Earth. An example of a square crater that has been thoroughly studied is Meteor Crater in Arizona.

Levoisier A (Astronominsk)
Among the better views of Levoisier A possible from Earth, situated as it is on the northwest limb of the Moon's nearside, in northwest Oceanus Procellarum, at the direct center of this image from a mosaic by Yuri Goryachko, Mikhail Abgarian and Konstantin Morozov, the Astronominsk team of Minsk, Belarus, sectioned from a full-disk observation photographed September 4, 2012 (below) [Astronominsk].
Levoisier A (Astronominsk)
Levoisier A is marked with an arrow in the full-disk, 4300 by 4900 mosaic of the waning Moon, September 4, 2012 [Astronominsk].
This crater formed on layers of sedimentary rocks that have orthogonal vertical joints running below where the crater formed. The joints disrupted the shock wave flow in certain directions, preventing the formation of a circular crater. Another indication of weaknesses within the target layers is the appearance of the northeastern portion of the crater rim. It appears as if a layer of rock has been peeled back.

Can you find the evidence of pre-impact fracturing (square boundaries) in the full resolution NAC, HERE?

Related Posts:
Squished Crater
Four of a Kind in Catena Davy

Wednesday, March 5, 2014

New views of Chang'e-3 from LRO

Four views Chang'e 3 landing site
Four recent LROC Narrow Angle Camera (NAC) views of the Chang'e 3 landing site: A) before landing, June 30, 2013; B) after landing, December 25, 2013; C) January 21, 2014; D) February 17, 2014. Each image is enlarged by a factor of two, each field of view is 200 meters across. Follow Yutu's path clockwise around the lander in panel D [NASA/GSFC/Arizona State University].
Mark Robinson
Principal Investigator
Lunar Reconnaissance Orbiter Camera (LROC)
Arizona State University

Chang'e 3 landed on Mare Imbrium (Sea of Rains) on 14 December 2013. LROC has now imaged the lander and rover three times: 25 December 2013 (M1142582775R), 21 January 2014 (M1144936321L), and 17 February 2014 (M1147290066R). From month-to-month the solar incidence angle decreased steadily from 77° to 45° (incidence angle at sunset is 90°); due to the latitude of the site (44.1214°N, 340.4884°E, -2630 meters elevation) the incidence angle cannot get much smaller. Solar incidence angle is a measure of the Sun above the horizon; at noon on the equator the Sun is overhead and the incidence angle is 0°, at dawn or dusk the incidence angle is 90°.

Four views of the Chang'e 3 landing site from before the landing until Feb 2014 [NASA/GSFC/Arizona State University].
As the Sun gets higher above the horizon, topography appears subdued and reflectance differences become more apparent. In the case of the Chang'e 3 site, with the Sun higher in the sky one can now see Yutu's tracks (February image). In the opening image you can see Yutu about 30 meters south of the lander, then it moved to the northwest and parked 17 meters southwest of the lander. In the February image it is apparent that Yutu did not move appreciably from the January location.

LROC February Chang'e 3 Site Image
LROC February 2014 image of Chang'e 3 site. Blue arrow indicates Chang'e 3 lander, yellow arrow points to Yutu (rover), and white arrow marks the December location of Yutu. Yutu's tracks can be followed clockwise around the lander to its current location. Image enlarged 2x, width 200 meters [NASA/GSFC/Arizona State University].
Owing to the lower solar incidence angle the latest NAC image better shows Yutu's tracks and the lander engine blast zone (high reflectance) that runs north-to-south relative to the lander. Next month the solar incidence angle will again increase and subtle landforms will begin to dominate the landscape.

LROC NAC Oblique Chang'e 3
LRO slewed 54° to the East on February 16 to allow LROC to snap a dramatic oblique view of the Chang'e 3 site (arrow).  Crater in front of lander is 450 m diameter, image width 2900 meters at the center M1145007448LR [NASA/GSFC/Arizona State University].

Some Related Posts and LROC Featured Images:
Geologic Characteristics: Chang'e-3 exploration region
ESA on Yutu, as controllers wait for Feb. 9 sunrise
Chang'e 3 Lander and Rover From Above
Safe on the Surface of the Moon
Recent Impact
Coordinates of Robotic Spacecraft

Saturday, March 1, 2014

Down the Montes Carpatus

Northern slope of unnamed mountain in Montes Carpatus range
Northern slope (top) of an unnamed mountain in Montes Carpatus. LROC Narrow Angle Camera (NAC) observation M186077208R, LRO orbit 12500, March 11, 2012; angle of incidence 18.28° at 1.04 meters resolution, from 132.3 km over 17.73°N, 331.11°E [NASA/GSFC/Arizona State University].
Hiroyuki Sato
LROC News System

Montes Carpatus is a mountain range composed of multiple peaks and rises along the southern edge of Mare Imbrium.

The bases of several peaks were flooded and are now surrounded by the mare basalts that fill the Imbrium basin. The opening image highlights the northern slope of an unnamed mountain in the range. The mountain is about 14 km in diameter at its current base, and its height is about 1700 meters.

Northern slope of unnamed mountain in Montes Carpatus range
Context view of LROC NAC M186077208R [NASA/GSFC/Arizona State University].
These low reflectance materials, which cover the broad top of this mountain, have over time cascaded down the northern slope. Similar low reflectance materials are distributed at the top of neighboring mountains of Montes Carpatus, but their origin is not clear. This region, including the Carpatus Mountains, was blanketed by ejecta from the impact that formed Copernicus crater. The ejecta thrown here from Copernicus may have contained pyroclastic materials, the dark volcanic products of explosive eruptions, or impact melt now exposed on the mountain slopes. Alternatively, dark pyroclastic materials were originally deposited atop these mountains.

New NAC and WAC images continue to present more detailed views of the Moon's surface, allowing us to read the complicated geologic history of the lunar mare.

Northern slope of unnamed mountain in Montes Carpatus range
A mountain that is part of Montes Carpatus is shown in a LROC WAC monochrome mosaic with WAC stereo (GLD100) topography overlain (red represents higher elevations and blue represents lower elevations); image center at 17.27°N, 331.33°E; the footprint of the NAC frame (blue square) and the location of opening image (yellow arrow) are indicated [NASA/GSFC/Arizona State University].
Explore the dark materials flowing down the mountain in full NAC frame, HERE.

Related Posts:
Alphonsus crater mantled floor fracture
A Dark Cascade at Sulpicius Gallus
Dark streaks in Diophantus crater
Dark Material Flows
Downhill Creep or Flow?
Layer of Pyroclastics
Rima Marius Layering
Dark Splash?

Tuesday, February 25, 2014

Dark patch enigma in Mare Smythii

Splash of dark material
Low reflectance materials splashed out from an unnamed crater, 1260 meter-wide field of view centered on 2.322°S, 81.725°E, incidence angle 3.3°   From an Narrow Angle Camera observation swept up over the far western interior of Mare Smythii, LRO orbit 19177, September 12, 2013. LROC NAC M1133662942L [NASA/GSFC/Arizona State University].
Hiroyuki Sato
LROC News System

Today's Featured Image highlights an unnamed fresh crater, about 700 meters in diameter, found on the western edge of Mare Smythii.

The low reflectance materials extend out in an distinctive bell shaped pattern from the southwestern edge of the crater rim. The interior crater wall near this deposit also shows splashes of relatively darker materials, as well as three other dark patches (at 12, 2, and 5 o'clock, relative to the crater center).

These deposits are likely similar in nature to the excavated dark deposits emplaced near the rim, and they appear to have partially flowed back into the cavity.

Full LROC NAC enigmatic splash in Mare Smythii
Enigmatic low reflectance material and surroundings in the context of the full 7.2 km width of LROC NAC observation M1133662942L [NASA/GSFC/Arizona State University].
Normally, ejecta travels radially from the impact center, resulting in lineations in the ejecta or rays pointing away from the source crater. In this bell shaped deposit, however, the two main dark lines outlining the bell are curved and extend about 150-200 m outside of the rim. Note that the surrounding terrain of this unnamed crater is nearly flat (see next WAC context); there are no readily apparent obstacles that might have affected the ejecta trajectory. Perhaps the original low reflectance deposits were unevenly buried, resulting in the curved dark patterns after excavation and final emplacement. What is the darker material? Since the crater is near the highland / mare boundary we might be seeing dark basalts or pyroclastics mixed with bright anorthositic crust.

Context LROC Featured Image, released February 25, 2014
Area of interest in LROC WAC monochrome mosaic (100 m/pix) overlayed by WAC stereo Digital Terrain Model (GLD100-DTM) false-color topography (red relatively high, blue low). Image centered at 2.22°S, 81.71°E. The LROC NAC M1333662942L footprint outlined in blue with the location of the LROC Featured Image above marked by the arrow [NASA/GSFC/Arizona State University]. 
Explore this enigmatic dark ejecta deposits in the full 7.2 km field of view of the NAC frame HERE, and find your own scenario.

Related Posts:
Dark Craters on a Bright Ejecta Blanket
Rima Bode: Constellation ROI
Dark-haloed crater in Mare Humorum
Dark halo crater
A Beautiful Impact
Pyroclastic Excavation
Dark Secondary Crater Cluster
Excavating Deposits

Friday, February 21, 2014

Taking a peek at Icarus

Icarus central peak (LROC NAC oblique)
The central peak of Icarus crater rising out of the shadows to greet a new lunar day! Image field of view approximately 10 km (north is at right. LROC NAC oblique mosaic M1124685518LR, LRO orbit 17914, June 1, 2013; spacecraft and camera slew 62.84° from nadir, resolution 3.3 meters per pixel and captured from 106.53 km over 5.58°S, 193.85°E [NASA/GSFC/Arizona State University].
H. Meyer
LROC News System

Icarus crater is one of a kind on the Moon; its central peak rises higher than about half its rim. Most central peaks rise only about halfway to the crater rim. Icarus' large, rounded central peak resembles that of Alpetragius on the eastern limb of Mare Nubium.

The disproportionate size of the central peak may be because both Icarus and Alpetragius are close in diameter to the transition between central peaks and peak rings.

LROC central peaks, wall and rim (LROC NAC oblique)
A reduced resolution image of the full NAC oblique looking from east to west across Icarus crater (5.348°S, 186.579°E). Notice the gentle slopes of the terraces on the crater wall and many superposed craters that suggest that Icarus is quite old. Icarus is approximately 94 km in diameter . LROC NAC oblique mosaic M1124685518LR  [NASA/GSFC/Arizona State University].
Icarus is located just west of Korolev crater on the lunar farside. Like the floor of Korolev, the floor of Icarus is covered with relatively smooth light plains material that can be seen outside the crater as well, filling not only crater floors but also the surface between craters in the highlands (See WAC context image below).

Icarus and vicinity (LROC WAC mosaic)
LRO WAC image of Icarus crater and vicinity (5.49°S, 186.74°E) in the lunar highlands. Image field of view approximately 365 km, Korolev crater and the Orientale basin are both east of this site [NASA/GSFC/Arizona State University].
Icarus (Kaguya PC) oblique
A "bonus" oblique assembly of Icarus crater, from a 100 km orbit, looking south, from the Planetary Camera collection from Japan's lunar orbiter SELENE-1 (Kaguya) [JAXA/SELENE].
These light plains were deposited during the formation of the Orientale basin, which is located over 1500 km away! The specific mechanism by which the light plains were emplaced is still under investigation, but the plains are likely made of ejecta produced during the formation of the Orientale basin.

See the full size NAC oblique HERE.

Related LROC Posts:
Stopped In Its Tracks
Overprinting Orientale
Crater Mendeleev

Wednesday, February 19, 2014

Oblique view of Hayn crater

Central peaks of Hayn crater (LROC NAC oblique)
Central peaks of Hayn crater, rising 1.5 km above the crater floor. Image is approximately 32 km across. LROC Narrow Angle Camera oblique mosaic M1105158497LR, orbit 15170, October 18, 2012; incidence angle 78.44° at a roughly estimated resolution of 4.7 meters per pixel. Spacecraft and camera slewed 57.46° east from nadir, 179.93 km over 68.01°N, 111.56°E [NASA/GSFC/Arizona State University].
H. Meyer
LROC News System

Hayn Crater (86.2 km, 64.55°N, 83.87°E) located just northeast of Mare Humboldtianum, is an exquisite example of a complex crater.

The central peak complex in the image above is dramatically illuminated by the low Sun casting long shadows across the crater floor.

The floor of Hayn crater contains spectacular remnants of the impact event: impact melt, slump blocks, and complex debris. In some areas, rocks on the floor have cracked and eroded into fields of boulders.

Oblique view of Hayn crater (LROC NAC)
A reduced resolution version of the full NAC oblique of Hayn crater (64.58°N, 83.89°E). Hayn is approximately 86 km in diameter. North at right; LROC Narrow Angle Camera oblique mosaic M1105158497LR, orbit 15170, October 18, 2012; incidence angle 78.44° at a roughly estimated resolution of 4.7 meters per pixel. Spacecraft and camera slewed 57.46° west of nadir, from 179.93 km over 68.01°N, 111.56°E [NASA/GSFC/Arizona State university].
In the full oblique image above, the walls of Hayn display large terraces that formed in the final stage of crater formation, called the modification stage. They are the surface expression of concentric listric faults.

Hayn-Humboldtanium basin (LOLA ILIADS)
Another, perhaps superfluous though certainly extraordinary, contexual view of Hayn with its emphasis on the crater's proximity with the Moon's north pole. LRO LOLA false color laser altimetry, at 128 points per pixel, through NASA's ILIADS application, a false perspective from 447 km over 55.3189°N, 78.7145°E, a point measured 4.127 km below mean global elevation (The image can be seen at its full size by clicking on it or HERE.) [NASA/GSFC/MSFC].
Hayn and Humboldtianum (LROC WAC)
LRO WAC image for context. Orthographic projection, field of view is approximately 220 km across [NASA/GSFC/Arizona State University].
These faults develop as the transient cavity undergoes gravitational collapse. The formation of terraces widens the crater cavity and shallows out the floor. This downward movement of the walls and floor is followed by uplift in the center as the crust accommodates the stress of the impact.



LROC Wide Angle Camera-derived digital terrain model showing Hayn is hemispheric context, orthographic projection centered on 60° East. Illustration to earlier LROC post "Craggy Peak, Impact Melts," January 12, 2012 [NASA/GSFC/Arizona State University].
Enjoy the exquisite full-resolution NAC oblique, HERE.

Related LROC Posts:
Craggy Peak, Impact Melts
Melt or Rubble?
View from the Other Side

Friday, February 14, 2014

LADEE's first images of the Moon

Series of LADEE star tracker images show the starfield against which the spacecraft baselines the data it collects eclipsed by the Moon below, as the short-lived mission's orbit skirts the northern edge of the Aristarchus plateau [NASA/ARC].
Rachel Hoover
NASA Ames Research Center

Earlier this month, NASA's Lunar Atmosphere and Dust Environment Explorer (LADEE) observatory successfully downlinked images of the moon and stars taken by onboard camera systems, known as star trackers. This is the first time the LADEE team commanded the spacecraft to send these pictures back to Earth.

The main job of a star tracker is to snap images of the surrounding star field so that the spacecraft can internally calculate its orientation in space. It completes this task many times per minute. The accuracy of each of LADEE's instruments' measurements depends on the star tracker calculating the precise orientation of the spacecraft.

"Star tracker cameras are actually not very good at taking ordinary images," said Butler Hine LADEE project manager at NASA's Ames Research Center in Moffett Field, California "But they can sometimes provide exciting glimpses of the lunar terrain."

Given the critical nature of its assignment, a star tracker doesn't use ordinary cameras. Star trackers' lenses have a wide-angle field of view in order to capture the night sky in a single frame.

The images shown here were acquired on February 8, 2014, around 2345 UT, while LADEE was carrying out atmospheric measurements. The series of five images were taken at one-minute intervals, and caught features in the northwestern hemisphere of the moon. LADEE was traveling approximately 100 km per minute along its retrograde semi-equatorial orbit. All images were taken during lunar night, but with Earthshine illuminating the surface.

The initial image captured the smooth-floored crater Krieger (22.86 km, 29.02°N, 314.39°E) on the horizon, with 7 km Toscanelli in the foreground.

The second image shows Wollaston P, about 4 km across near the horizon, and the southeastern flank of the lunar mountain Mons Herodotus.

The third image caught a minor lunar mountain range Montes Agricola, the northwest frontier of the Aristarchus Plateau, as well as the flat-floored crater Raman, about 10 km in diameter.

Image four in the series captures 6 km Golgi and 5 km Zinner.

The final image views craters Lichtenberg A (6.9 km, 28.9°N, 299.89°E) and Schiaparelli E (4.9 km, 27.12°N, 297.93°E) in the smooth mare basalt plains of western Oceanus Procellarum.

LADEE (nomenclature)
Location of LADEE Star Tracker Cameras in relation to its primary components [NASA/LEAG].
The star trackers will operate while LADEE continues to measure the chemical composition of the atmosphere, collect and analyze samples of lunar dust particles in the atmosphere and hope to address a long-standing question: Was lunar dust, electrically charged by sunlight, responsible for the pre-sunrise glow above the lunar horizon observed during several Apollo missions? And who knows? The star trackers may help answer that question.

Thursday, February 13, 2014

Overprinting Orientale

Overprinting Orientale
Fractured crater draped with ejecta from the impact event that created the Orientale basin, south of Buffon crater (downslope to the right). Crop from LROC NAC oblique mosaic M1128039712LR, LRO orbit 18386, July 9, 2013; 74.2° angle of incidence, resolution very roughly 2.3 meters, spacecraft and camera slewed 65.27° toward the east, from 58.43 km over 46°S, 222.48°E  [NASA/GSFC/Arizona State University].
J. Stopar
LROC News System

This spectacular oblique view looks from west to east across an area south of Buffon crater (45.715°S, 229.052°E) that is draped with impact ejecta from the Orientale Basin.

Orientale ejecta to have flowed over a pair of modified craters (each approximately 16 km in diameter, also see image at far bottom). Because the ejecta is superposed on top of the craters and appears to flow over much of the scene, the ejecta should be younger than the craters. However, these craters do not exhibit typical morphologies, and neither does the Orientale ejecta! Just how did this spectacular scene form?

Overprinting Orientale
Full width NAC oblique image of Orientale ejecta covering the local terrain. Ejecta and crater floors are lumpy and crisscrossed by numerous graben. A flat lying mare pond is located just below center on the right side of the image (arrow). Scene is approximately 41 km in height, oblique view, west to east. Click image or HERE to view larger image [NASA/GSFC/Arizona State University].
First, the pair of prominent craters seen above have concentric, mounded or lumpy looking floors. This morphology is atypical of impact craters of this size (see Steno Q or Burg crater for more typical examples), but is reminiscent of many floor-fractured craters (such as Atlas or Komarov), which are thought to form through uplift caused by magma intruding deep beneath the surface. However, the graben seen in the examples above are more subdued those in most floor-fractured craters, suggesting that they may be blanketed by the overlying Orientale ejecta.

There is also a small pond of basalt (darker and flat) exposed just below the center on the right side of the full width image (above). This is a tell-tale sign of volcanic activity in the area, lending support to the hypothesis that the lumpy craters were modified by magma from below. This, however, does not prove which occurred first: the volcanism or the emplacement of the Orientale ejecta.

Overprinting Orientale
LROC Wide Angle Camera (WAC) mosaic of the area south of Buffon crater. Blue polygon highlights approximate boundaries of the area shown in the featured oblique Narrow Angle Camera (NAC) frame; arrow indicates location of impact melt flow featured in a previous post. The ejecta within the blue polygon is fractured and warped, but the ejecta indicated by the arrow is not [NASA/GSFC/Arizona State University].
The final observation that informs the sequence of events is the occurrence of similar graben in both the crater floors and the adjacent ejecta outside the craters that is not typical of Orientale ejecta in this region. The previous post Stopped in its Tracks featured a nearby Orientale ejecta deposit located only 30 kilometers west of today's spectacular image; that ejecta is not crisscrossed by graben like those seen in the opening image above! Thus, volcanic activity in this area may have occurred after the large impact event that formed the Orientale basin around 3.8 billion years ago. However, further analysis and age dating in this area are needed before we can say for certain that the Orientale ejecta was modified (or overprinted) by younger volcanism.

Overprinting Orientale
Detail of Orientale ejecta, showing inferred direction of flow towards the mare unit shown in the larger images above [NASA/GSFC/Arizona State University].
Try to unravel the sequence of events on display in the full oblique image, HERE.

Related Posts:
Ground Hugging Ejecta
Fall Out
Orientale Sculpture
The Fractured Floor of Compton
A Colorful History of Floor-Fractured Komarov

Wednesday, February 12, 2014

First Science from LADEE, LPSC 2014 (March 18)

45th Lunar and Planetary Science Conference
Lunar Dust and Exosphere -
The First Results from LADEE
The Woodlands, Texas
Tuesday morning, March 18, 2014

Richard Elphic and Andrew Poppe, Chairs

Special Session on Lunar Dust and Exosphere Featuring the First Results from LADEE:   This session will address new results concerning the lunar exosphere, the mystery of electrostatically lofted dust, and other new research concerning the exotic phenomena surrounding the nearest example of a surface boundary exosphere. The focus will be on results from the Lunar Atmosphere and Dust Environment Explorer (LADEE) mission, but will also incorporate relevant Lunar Reconnaissance Orbiter (LRO) exosphere/dust measurements and ARTEMIS observations related to LADEE science.

LADEE on Clementine star-tracker horizon glow
Notional view of the LADEE spacecraft superimposed on Clementine star-tracker imagery from 1994 [NASA/DOD/JPL-Caltech].
8:30 a.m. Elphic, Hine, Delory Salute and Noble, et. al. - The Lunar Atmosphere and Dust Environment Explorer (LADEE): Initial Science Results, #2677

LADEE is making measurements of the tenuous lunar exosphere and the dust cloud from meteoroid impacts. The talks presented in this special session will highlight LADEE’s preliminary science results. These include initial observations of argon, neon and helium exospheres, and their diurnal variations; the lunar micrometeoroid impact ejecta cloud and its variations; spatial and temporal variations of the sodium exosphere; and observations of sunlight extinction caused by dust, as well as other topics.

8:45 a.m. Glenar, Stubbs and Elphic - LADEE Search for a Dust Exosphere: A Historical Perspective, #2640

The LADEE search for a dust exosphere is discussed in the context of recent dust upper-limit measurements. In general the detection of a small-grain dust population consistent with the low Clementine and LAMP upper limit estimates will be a challenge for the LADEE mission. On the other hand, these prior measurements represent only a small part of the LADEE search space, and none coincide with the occurance of major meteor streams. The LADEE dust search is sure to produce surprises.

9:00 a.m.  Horanyi, Gagnard, Gathright, Gruen and James, et al. - The Dust Environment of the Moon as Seen by the Lunar Dust Experiment (LDEX), #1303

The Lunar Dust Experiment (LDEX) onboard the LADEE mission continues to make observations in lunar orbit since its cover was deployed on October 13, 2013.

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Figure 2.  Summary of LADEE/LDEX activities through January 3, 2014. The number of recorded events (noise and dust impacts) sharply increased following LADEE orbit lowering maneuvers. An unusually large burst of events was observed November 12, most likely related to the Taurids meteor stream, and the following intense period, starting December 13, coinciding with the Geminids and the landing of Chang’e-3.

9:15 a.m.  Kempf, Grün, Horanyi, James and Lankton, et al. - Observations of the Lunar Dust Exosphere with LDEX, #1389

This talk will report about first insights into the properties of the lunar dust exosphere based on a preliminary analysis of the LDEX data. The transmitted data set is already larger than any other existing observation of a dust exosphere by orders of magnitudes and deepened our insight into the physics of this important phenomenon. This talk will report about first insights into the properties of the Lunar dust exosphere based on a preliminary analysis of the LDEX data.

9:30 a.m.  Stubbs, Glenar, Wang, Hermalyn and Sarantos, et al. - The Impact of Meteoroid Streams on the Lunar Atmosphere and Dust Environment During the LADEE Mission, #2705

We describe the 18 annual meteoroid streams predicted to encounter the Moon during the LADEE mission, and discuss the implications for the lunar environment.

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Figure 1. Locations of radiants for 18 annual meteor streams at the time of peak activity plotted as Selenographic Solar Ecliptic (SSE) latitude and local time. The points are color-coded to show the Zenith Hourly Rate (ZHR) at the peak in shower activity. (ZHR is the hourly rate of meteors seen by standard a observer on the Earth under optimum viewing conditions.) For our purposes ZHR serves as rough guide to meteoroid flux rates incident at the Moon. Only six of the 18 streams have peak ZHR exceeding background HR so it is reasonable to assume these streams will likely have the most noticeable effects on the lunar environment compared with typical conditions. (Gray shading covers the latitudinal range of the LADEE orbit.)

9:45 a.m.  Halekas, Poppe, Delory, Elphic and Angelopoulos, et al. - ARTEMIS Observations and Data-Based Modeling in Support of LADEE, #1548

LADEE with ARTEMIS P1 and P2
Relative positions of the LADEE with the ARTEMIS P1 and P2 spacecraft early on December 23, 2013 [NASA/JPL-CalTech].
The goal of the LADEE mission is to understand the exosphere of the Moon, including its structure, temporal variability, and sources and sinks. To achieve this goal, we must determine how exospheric dust and neutrals behave, not in isolation, but as part of an inextricably coupled system that includes the surface and the plasma environment.

Jasper Halekas schematic of lunar ionosphere
A schematic of the very dynamic lunar ionosphere put together originally by Jasper Halekas, now an investigator with the ARTEMIS program.
Charged particles, their interactions with the surface, and the electric and magnetic fields that they produce and respond to, contribute to source and sink processes for both lofted dust and exospheric gases, and therefore to their spatial and temporal structure and variability. The LADEE payload does not include plasma instrumentation; instead, we utilize a combination of ARTEMIS measurements of upstream plasma parameters and data-based modeling to determine plasma quantities around the Moon, including at the LADEE orbit and in the regions covered by UVS scans and those providing the source populations ultimately measured by LDEX and NMS.

The ARTEMIS (Acceleration, Reconnection, Turbulence, & Electrodynamics of Moon’s Interaction with the Sun) mission consists of two probes from the heliospheric constellation THEMIS retasked to the Moon in 2011. ARTEMIS provides comprehensive measurements of charged particles and magnetic and electric fields around the Moon from a two-point vantage that enables continuous upstream plasma monitoring.

ARTEMIS P1 and P2
Early representation from the highly innovative proposal to gradually reposition two of the five member constellation of THEMIS probes into lunar orbit, where today they operate as ARTEMIS P1 and P2.  On the way to being re-tasked, the vehicles became the first to orbit the Earth Moon Lagrange points L1 and L2.  Their functions are presently an important part of the LADEE mission.
The two ARTEMIS probes currently reside in stable near-equatorial elliptical orbits. An orbital design targeting periapses near the lunar dawn terminator.

The ambient plasma, directly and through its control of the nearsurface electrostatic environment, contributes significantly to the exospheric cycle. By comparing various measurements, and utilizing ARTEMIS-measured fields to determine their trajectories and likely sources, we can obtain additional constraints on the sources, composition, and dynamics of the tenuous lunar atmosphere..

10:00 a.m.  Szalay, Horanyi, Poppe and Halekas - LDEX Observations and Correlations with ARTEMIS Measurements, #1500

ARTEMIS provides a variety of plasma measurements which show a high degree of correlation with LDEX current measurements. There are two regions in the LDEX data that show consistent correlation: 1) the subsolar point and 2) the time LADEE crosses into umbral shadow.

Shown in Figure 3 are the average LDEX current for 15 minutes from subsolar and shadow crossing time respectively. Additionally, the component of the convection electric field parallel to the LDEX boresight appears to be significant in LDEX’s current measurements and will be discussed in this presentation.

This talk will focus on the correlations between LDEX and ARTEMIS data.

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Figure 2. - LDEX current measurements. Above: Orbit with high LDEX current variability, and bottom: Quiet period in LDEX current data.
10:15 a.m.  Poppe, Halekas, Szalay, Horanyi and Delory - Model-Data Comparisons of LADEE/LDEX Observations of Low-Energy Lunar Dayside Ions, #1393

The lunar exosphere is a tenuous, collisionless combination of various neutral species derived from a variety of sources, including charged particle sputtering, micrometeoroid impact vaporization, internal gas release, and photon-, electron-, and thermally-stimulated desorption. Solar irradiation will photoionize these neutrals which are in turn picked up by the ambient interplanetary magnetic and electric fields and lost to interplanetary space.

The Lunar Dust EXperiment (LDEX) onboard the Lunar Atmospheric and Dust Environment Explorer (LADEE) is currently searching for the signature of charged, sub-micron sized dust grains lofted to kilometer altitudes above the lunar surface, but such measurements are also sensitive to ambient, low-energy ions including those of lunar exospheric origin.

The LADEE Lunar Dust Experiment (LDEX)
We model the response of the LADEE/LDEX instrument to low-energy lunar dayside ions and discuss implications for the lunar exosphere and ionosphere.

10:30 a.m.  Benna, Mahaffy and Hodges - Early Results from Exospheric Observations by the Neutral Mass Spectrometer (NMS), #1535

We present early observations of He, Ar, and Ne observations from the LADEE NMS in lunar orbit. The Neutral Mass Spectrometer (NMS) of the Lunar Atmosphere and Dust Environment Explorer (LADEE) Mission is designed to meas-ure the composition and variability of the tenuous lunar atmosphere. The NMS complements two other instru-ments on the LADEE spacecraft designed to secure spectroscopic measurements of lunar composition and in situ measurement of lunar dust over the course of a 100-day mission in order to sample multiple lunation periods.

Instrument activities are designed and scheduled to provide time resolved measurements of Helium and Argon and determine abundance or upper limits for many other species either sputtered or thermally evolved from the lunar surface.

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Figure 3. Evolution of Helium abundance (in instrument counting units) as a function of solar local time observed during the LADEE commissioning phase.
Early Results From NMS Observations: Owing to its very low chemical background the NMS instrument was successful at detecting and mapping exospheric Helium during the high altitude (250 km) commissioning phase. This early mapping campaign provided the unique opportunity to observe variation of Helium at a constant altitude, for nearly a full lunation. Figure 3 shows results of Helium spatial and temporal variability as the Moon moves in and out of the Earth’s magnetotail.

LADEE Neutral Mass Spectrometer (NMS)
At the end of the commissioning phase and after the orbit’s periselene was lowered to approximately 50 km, the NMS was able to detect Argon and Neon.


10:45 a.m.  Colaprete, Elphic, Landis, Karcz and Shirley, et al. - Overview of the LADEE Ultraviolet-Visible Spectrometer: Design, Operations, and Initial Results, #2566

This talk will overview the design, performance, and initial results of the LADEE UVS instrument.

UVS deployed its limb-viewing telescope door on October 17 and began a series commissioning activities, including pointing, wavelength and preliminary radiometric calibrations. UVS made its first lunar limb observations on October 23, 2013.

UVS has been routinely monitoring two previously measured atmospheric species, potassium and sodium, and has been making observations to search for other, previously sought species including OH, H2O, Si, Al, Mg, Ca, Ti, and Fe. UVS is also able to detect the scattered light from lofted dust between the altitudes of a few km up to 50 km using its limb telescope, as well as search for dust very near the surface using solar occultation measurements. The UVS instrument operates between 230 – 810 nm with a spectral resolution of less than 1 nm. The spectrometer has been operating nominally.

LADEE ultra-violet - visible light (UVVIS) spectrometer (UVS)
Limb observations, using the UVS three-inch telescope, have been made on a routine basis, with limb “stares” at 20 km at the terminators, and 40 km at around local noon time. At the terminators the spacecraft “nods” the telescope between the surface and about 50 km. At noon it was found that near-surface scatter precluded observations below about 30 km, so nods are not performed then. There have been a mix of both “backward” looks (stares that point in the anti-velocity direction of the spacecraft), and “forward” looks (which flip the spacecraft to allow UVS to look in the velocity direction). This permits observations both in and away from the direction of the sun.

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LPSC-2014, #2518 - Figure 1.  Schematic of a LADEE “nod” operation to detect dust and gases at the lunar limb with the UVS. Nod begins in the stare orientation, scans down to lunar surface, up to higher altitudes, then back to stare. This activity provides science data at many altitudes down to lunar surface. The telescope can also be pointed 180° opposite from normal Limb stare orientation to allow for observations in forward scatter at sunset terminator.
Occultations have been performed about once every two days, tracking the sun as it sets behind the sunrise terminator between about 35 km and the surface. In this mode UVS has gathered spectra at a rate of either 15 msec or 26 msec, corresponding to a spatial sampling of less than 1 km with very high SNR (typically less than 500 for a single scan).

Sodium and potassium are regularly measured in all activities, except for occultations. Trends in these measurements are made both spatially and temporally, and associations are with specific events, such as meteor streams, and surface composition are examined.

11:00 a.m.  Hermalyn, Colaprete, Elphic, Landis and Karcz, et al. - Impact Lofted Ejecta Contribution to the Lunar Exosphere: Experiments and Results from the LADEE Ultraviolet Visible Spectrometer, #2518

This study presents preliminary results of lunar limb observations from the UVS on LADEE toward understanding the impact contribution to the dust exosphere.

“Larger” impact events (e.g., impactor size>>target grain size), which are expected to form sporadically over the course of a year, are capable of lofting a considerable amount of material for a measureable period of time. As these ejecta return to the surface (or encounter local topography), they impact at hundreds of meters per second or higher, thereby “scouring” the surface with low-mass oblique dust impacts. While these high-speed ejecta represent only a small fraction of the total ejected mass, the lofting and subsequent ballistic return of this dust has a high potential for mobilization.

The actual visibility of these ejecta clouds diminishes with height and time as the particles spread ballistically.

Given the amount of material expected to be lofted above 5km, these results indicate that there is a significant chance of LADEE observations of a primary ejecta cloud even from relatively small impacts- if they occur at the right time and place (e.g., at a location and recently enough to enter the fields of view of the instruments before spreading too much).

The chances of observing such an event grow significantly higher during a meteor shower, which have been observed to cause very frequent impact flashes on the moon. around the moon for durations of several hours. These smaller, more frequent, craters can loft diminished (but measurable with the UVS & LDEX instruments) amounts of regolith for tens of minutes.

11:15 a.m.  Wooden, Cook, Colaprete, Shirley and Vargo, et al. - LADEE UVS Observation of Solar Occultation by Exospheric Dust Above the Lunar Limb, #2123

LADEE UVS solar occultation measurements (40–0 km altitudes) reveal spectral signatures of forward scattering and absorption by dust in the lunar exosphere.

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Figure 1. (a) UVS solar viewer foreoptics, showing six sequential baffles, which define the field of view and minimize the contribution from off-axis scattered light. The solar diffuser is shown just before the fiber optic input, which leads to the spectrometer. (b) Schematic of an UVS occultation session showing the solar viewer field of view cone, grazing the lunar exosphere and subsequently the lunar limb, as LADEE’s orbit progresses through local sunrise.
Light curve extinction by duct grain occultation
Figure 2. A light curve from an example occultation activity, annotated with cartoons of the Sun as seen from the UVS solar viewer. The yellow line around the Sun in each cartoon marks the solar viewer field of view. Each view corresponds to a different section of the solar occultation light curve.
Our preliminary results indicate wavelength dependent extinction as a function of altitude. We attribute the detected spectral color changes to the presence of sub-micron sized dust grains in the lunar exosphere. Details of these results will be presented, and compared to previous models of the lunar dust exosphere.

11:30 a.m.  Hurley, Benna, Mahaffy, Elphic and Colaprete, et al. - Upper Limits on the Propagation of Constituents of the Chang’e-3 Exhaust Plume from LADEE Observations, #2160

The native lunar exosphere is sparse. The estimated total mass of the lunar exosphere is ~107 g, with a source rate of ~10 g/s.  Landing a vehicle such as the Chinese Chang’e-3 lander on the surface of the Moon would require burning an estimated 106 g of rocket fuel over ~12 minutes.

Thus, the introduction of vapor into the lunar environment via rocket exhaust during a soft lunar landing constitutes a 100 times temporary enhancement to the source rate to the lunar exosphere and an increase in the total mass of 10%. Whereas the native lunar exosphere is comprised primarily of helium and argon; the rocket exhaust comprises water, carbon dioxide, ammonia, and other HCNO products.

The distribution of particles in the lunar exosphere is largely controlled by the interactions between the particles and the lunar surface. For example, helium does not stick to lunar regolith grains, thus follows an inverse relationship between the density and the surface temperature. In contrast, argon does stick to the surface at colder, nightside temperatures. Argon density is observed to peak at the terminators.

Thus, if the propagation of the exhaust vapors can be monitored, it can reveal previously unknown properties of the gas-surface interaction with the lunar regolith.  We model the release and propagation of the exhaust gases on the Moon and compare to observations in orbit around the Moon from the Lunar Atmosphere and Dust Environment Explorer (LADEE) spacecraft.

12:00 p.m. To be Announced.


For further information about the 45th Lunar and Planetary Science Conference visit:
http://www.hou.usra.edu/meetings/lpsc2014/